package y23.Nov;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;

public class Test8 {
    public static void main(String[] args) {
        Scanner  scanner = new Scanner(System.in);
        while(scanner.hasNext()){
            int a = scanner.nextInt();
            int b = scanner.nextInt();
            double bq = 0;
            List<Integer> list = new ArrayList<>();
            int k = scanner.nextInt();
            for (int i = 0; i < k; i++) {
                Random random = new Random();
                list.add(random.nextInt(a+b));
            }
            for (int i = 0; i < list.size(); i++) {
                if (list.get(i)<a){
                    bq++;
                }
            }
            double x = bq/list.size();
            System.out.println(x);
        }
    }
}
